Portable sonar system

ABSTRACT

The patent disclosure presented herewith is directed to an improved sonar system to be worn by swimmer-diver personnel having as its salient features an improved transducer assembly for establishing a plurality of investigative beam patterns; a phase detector arrangement for eliminating spurious echo returns; and a high resolution visual display adapted to be worn by the swimmer diver user of the system.

Rolle Mar. 26, 1974 PORTABLE SONAR SYSTEM 3,555,500 1/1971 Longerich etal 340/3 [75] inventor: Albert L. lRolle, Panama City, Fla.

[22] Filed: May 6, 1970 [21] Appl. No.1 34,923

Primary Examiner-Richard A. Farley Attorney, Agent, or Firm-Richard S.Sciascia; Don D. Doty; Richard S. Sciascia [5 7 ABSTRACT The patentdisclosure presented herewith is directed to an improved sonar system tobe worn by swimmer- 52 105.01 340/3 R diver Personnel having as ssalient features an 51 int. cu. G015 9/68 Proved transducer assembly forestablishing a plurality [58] Field of Search 340/3 R of investigativebeam p ns; a phase detector a rangement for eliminating spurious echoreturns; and [56] References Ci d a high resolution visual displayadapted to be worn by UNITED STATES PATENTS the swimmer diver user ofthe system.

3,506,953 4/1970 Rudy 340/3 10 Claims, 22 Drawing Figures w i [b 4:

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4 ill/ PORTABLE SONAR SYSTEM STATEMENT OF GOVERNMENT INTEREST Theinvention described herein may be manufactured and used by or for theGovernment of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION This invention pertains to an echo typeranging and detection system. More particularly, the invention pertainsto an underwater acoustic ranging and detection system. By way offurther description, but not by way of limitation, the invention ischaracterized as a swimmer carried sonar system.

There are few sonar systems which may be carried by a swimmer. The mostsuccessful prior art type of sonar for swimmer use has a narrowinvestigative beam pattern which is aimed by the user to obtain azimuthinformation. The range of the target is determined by judging thefrequency of an aural tone. In this system, there is no visual display.

A system such as the aforedescribed prior art system, without visualdisplay, is difficult to use because most swimmers depend upon visualstimuli in their underwater activities. In areas where theswimmer-divers work about marine ordinance or sunken structures, therehas been a need for a system with a higher resolution that has beenavailable heretofore and, thus, there has been a need for a visualdisplay to effect such resolution.

SUMMARY OF THE INVENTION As will be more completely explained, theinvention provides a high resolution sonar system of compact dimensionalparameters suitable for use by swimmer personnel engaged in underwateractivities. The sonar system of the invention provides a B scan visualpresen tation and is useful in orienting the swimmer with respect tounderwater objects, other swimmer personnel, and the sea floor;therefore, it obviously constitutes a meritorious advance in the art.

Accordingly, it is an object of this invention to provide an improvedswimmer carried sonar system.

A further object of this invention is the provision of side scanningtype of sonar system of compact dimensions.

A further object of this invention is to provide a sonar system with areadout for selection of sonar readout and visual perception combined orsonar readout only.

A further object of this invention is the provision of a swimmer carriedsonar system with a viewing mask readout.

Another object of this invention is the provision of an improved sonarsystem employing a staggered beam transducer assembly.

A further object of this invention is the provision of a compact sonarsystem employing an improved phase detection means.

Other objects and many of the attendant advantages will be readilyappreciated as the subject invention becomes better understood byreference to the following detailed description, when considered inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing the system ofthe invention in use;

FIG. 2 is an illustration of the preferred form of a control unit, acomponent part of the invention;

FIG. 3 is an elevation view of the transducer assembly used in theinvention;

FIG. 4 is a diagrammatic showing of the hydrophone orientation used inthe invention;

FIG. 5 is a diagrammatic showing of the projector transducer orientationused in the invention;

FIG. 6 is a diagrammatic showing of a single projector pattern inrelation to adjacent hydrophone patterns, as used in the invention;

FIG. 7 is a diagrammatic showing of how a plurality of hydrophone andprojector patterns cooperate to provide a composite scanningarrangement;

FIG. 8 is a plan view showing the relation of ensonified zones of thesea bottom and a target object lying thereon;

FIG. 9 illustrates a preferred hydrophone transducer arrangement;

FIG. 10 is a front view of the viewing mask assembly according to theinvention, as it is worn by personnel using the system of the invention;

FIG. 1145 a sectional view taken along line llll of FIG. 10 andillustrates the optical portion of the readout according to theinvention;

FIG. 12 is a block diagram of the circuitry of the sonar of theinvention;

FIG. 13 is a schematic representation of an alternate circuitarrangement for the visual readout of the instant invention;

FIG. 14 is a diagrammatic illustration of the transmit multiplex andpower amplifier circuit component of the instant invention;

FIG. 15 is a diagrammatic showing of an alternate arrangement for thetransmit multiplex and power amplifier circuit component of theinvention;

FIG. 16 is a showing in block diagram form of the receiver multiplexcircuit componet of Applicants invention;

FIG. 17 is a block diagram showing a preferred embodiment of thecounter-programmer circuit of Applicants invention;

FIG. 18 is a circuit diagram of the bistable delay and phase detectorcircuits of the system of the invention;

FIG. 19 is an illustration of electrical waveforms taken from indicatedpoints shown in FIG. 18;

FIG. 20 is a schematic showing of a monostable multivibrator circuitcomponent according to invention;

FIG. 21 is a block diagram showing of a quadruple NAND component used inthe system of the invention; and

FIG. 22 is a schematic showing of the circuit arrangement of one of theNAND gates used in the quadruple NAND gate shown in FIG. 21.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 there isshown an underwater diver 21 approaching a submerged object 22. Aconventional back mounted life support system 23 provides a mounting foran electronics and battery package 24, a component of the invention.Diver 21 wears a viewing mask 25 which has provisions for a visual sonardisplay. Mask 25 is connected to instrument package 24 by a suitableconnecting cable 26, which may comprise a fibre optic light transmissiondevice. Diver 11 controls the sonar system from a hand held control unit27 which is, likewise, joined to battery electronics package 24 bysuitable cable means 28.

Referring to FIG. 2, hand held control unit 27 is seen to comprise acylindrical body portion 29. Switch panel 31 on the upper surface ofbody portion 29 is positioned to be accessible to the thumb of hand ofdiver 2l grasping control unit 27. Switches 32, 33, and 34 are mountedin switch panel 3ll for the control of the various functions of thesystem, as will be explained herein. A control ring 35 may be rotated toprovide continuous adjustability for some functions such as gain ordisplay intensity. One such control is shown, but it should beunderstood that more may be provided, if desired. A plate 36 at theforeward end of body portion 29 mounts a transducer assembly 37.

It will be observed that plate 36 is angularly mounted relative to theaxis of body portion 29 of control unit 27. This arrangement permits adiver swimming horizontally to scan the bottom beneath him and determinehis height thereabove. In this application, the system of the inventionis especially useful in swimmer navigation, in turbid waters, or indarkness. Further, it should be noted that a fastening means, not shown,may be provided to attach control unit 27 to the clothing of diver '21and thereby free both hands for swimming.

Referring to FIG. 3, it will be seen that transducer assembly 37comprises both receiving hydrophone array 38 and projector transducerarray 39. Hydrophone array 38 comprises eleven electroacoustictransducers 31, to be more completely described herein, which aremounted on angularly faced mounting pedestal 42. Similarly, transducerarray 39 comprises electroacoustic transducers 43 mounted on angularlyfaced mounting pedestal 44. Pedestals 42 and 44 are attached to a commonbase support 45 so as to extend perpendicularly upwardly therefrom. Asshown in FIG. 3, arrays 38 and 39 are located adjacent to one anotherand may be encapsulated in a suitable material to form an enclosure 46thereabout. Pedestals 42 and 44 are hollow and provide housing means forsome of the circuitry of the invention.

Such an encapsulation constitutes only one type of housing arrangementfor transducer arrays 38 and 39. Other constructions may be employed, ifdesired. One type of housing considered useful in swimmer carried sonarsystems employs a fluid filled enclosure to surround transducer arrays.It should also be noted that the fluid filled enclosure may, if desired,comprise an acoustic lens.

As may be better understood with reference to FIGS. 4 and 5, theindividual hydrophone transducers 41 are angularly displaced from oneanother by an angle a. The projector transducers 43 are similarlyangularly oriented with respect to one another and are separated by thesame angle 0:. However, the transducers are arranged such that a givenprojector transducer 43 makes an angle with respect to base support 45to bisect the angle made by two adjacent hydrophone transducers 41located in the hydrophone array 38.

The resulting transmission and reception patterns for a projectortransducer and associated hydrophone are shown at FIG. 6. Projectorpattern 47, shown by the solid line, is typical of the pattern producedby a linear array. I-Iydrophone patterns 48, shown by broken lines, arelocated on either side of projector pattern 47 and are equally spacedtherefrom. The directivity patterns cooperate, when used together, toproduce a narrow directivity with respect to the reference axis 49corresponding to the linear direction of the pair.

Referring to FIG. 7, there is shown diagrammatically how a plurality oftransducer combinations found in transducer assembly 37 are combined toform a sector scan. As may be seen, projector patterns 47 are positionedbetween two receiver patterns 48. From the figure, it is readilyapparent that N projectors and N+l transducers may be switched toproduce a sector scan of 2N sectors. Of course, the greater the numberand the smaller the beamwidth of the sectors, the higher will be theresolution of the system.

For the device of the invention, ten projector transducers 43 are usedin combination with eleven hydrophone transducers 41. These arrangementsare switched by means of suitable circuitry, to be more fully describedherein, to provide twenty composite transmit and receive channels to beestablished using but 10 projectors. Each pattern is a composite of thepatterns generated by one projector pattern 47 and one hydrophonepattern 48. The two patterns combine in the well understood fashion toproduce a composite pattern which is the product of the individualpatterns. This resultant pattern has a narrow, highly directive patternwith greatly reduced side lobes in comparison with the patterns of theprojector or the hydrophone.

Referring to FIG. 7, it may be seen how the respective patternscooperate to produce the desired scan area. Projector pattern 47 firstcooperates with hydrophone pattern 48 to produce a first scan, and thenwith hydrophone pattern 48 to produce a second scan. Next, projectorpattern 47' cooperates with hydrophone pattern 48 to produce a thirdscan, and then with hydrophone pattern 48" to produce a fourth scan. Theprocess is carried on with the following projector and hydrophonepatterns until the sequence is complete with projector pattern 47"cooperating with hydrophone pattern 48" to produce the final scan. Inthe developmental studies of the invention, each individual pattern isassumed to be B degrees wide so that the resulting composite pattern is23/3 degrees wide.

The entire sector covered is 4nB/3 degrees wide. Practical values forBare in the range of 1 to 5 and n may be between 10 and 40. It should benoted that the angular spacing of the patterns preferably results in anangular redundancy in the total composite scan pattern.

The angular overlap of adjacent composite patterns permits the rangingsystem of the invention to provide a more accurate relative bearing andrange information than prior art systems having the same number oftransducers. That is, to obtain the narrow composite beamwidth the sametransducer had to be used for transmitting as well as receiving orelaborate shading arrangements were required. This improvment isparticularly useful in determining the relative range and position of anobject having an angular size which is relatively large in comparison tothe composite pattern employed by the system, and having a relativelylarge surface lying at an angle to the acoustic axis of the compositesector. Such a target is presented by object 22 in FIG. 1.

Referring to FIG. 8, the parameters involved in detection and ranging ofobject 22 with an angularly disposed leading edge 54 are more clearlyshown. The fig ure illustrates a single composite pattern with thedivergence thereof exaggerated for purposes of explanation. At anyinstant, the target returns may be considered to originate from a stripwhich is AR wide and of a length which is a function 8 of the range R.The three strips 51, 52, and 53 illustrated may be considered portionsof the bottom ensonified by successive pulses directed along a commonacoustic axis 55, or by a single pulse at three separate instants oftime. When the ensonified zone encounters a solid object, such as object22, a shadow zone is formed which limits the length of the strip 53 atranges greater than the range of edge 54.

If the ranging sonar is only equipped to process amplitude information,the reverberation echo from strip 53 will be displayed on a bearingcorresponding to acoustic axis 55. In the illustrated instance, thereturn would be displayed in the shadow zone where no returns actuallyoriginate. In the device of the invention this would result in a brightline, of a length corresponding to the 2 composite radiation pattern ofthe preferred embodiment of the invention, displayed as centered onacoustic axis 55. A detection system which would display the echo returnfrom strips 51, 52, and 53 on their respective centers would improve theresolution of the edge 54.

A sonar system that measures the difference in time of arrival of thereturn signal at two spaced hydrophones located in a side-by-siderelationship will display the return centered on the bearing azimuth tothe center of reflection of the particular strip from which thereflected signal originates. A phase detector is capable of providingthis type of signal processing, and, for this reason, is incorporated inthe circuit arrangement of the invention. It should be made clear thatthe exact position of the display is dependent upon the number anddistribution of the scattering elements in the strip from which the echooriginates. The echo return is displayed centered on the bearing of theapparent acoustic center of gravity i.e., the mean energy distributionof the strip. It should not be supposed, however, that the phasedetection is able to resolve individual ones of these scatters which arenot resolved in range.

H0. 9 illustrates how the individual hydrophone transducer may beconfigured to produce the aforesaid highly desirable results. It will beobserved that hydrophone transducer 41 comprises a piezoelectric plate56. An electrode 56 is attached to one side thereof and is coextensivetherewith. Conductor 56 makes electrical contact with electrode 57 andprovides electrical connection to the transducer from the remainder ofthe circuitry. A plurality of grooves 59 are cut into plate 56 toeffectively form thereon a plurality of posts 61 extending upwardly fromthe uncut portion of plate 56. In the example shown there are 44 posts61. Electrodes 62 are affixed to the upper face of each post 61 forelectrical contact therewith. Electrical conductor 63 joins eighteenalternate posts 61 starting at the right end of transducer M andconductor 6d joins an identical number of alternate posts til startingat the left end thereof. The two groups of posts comprise, in effect,two transducer arrays. The two arrays are separated acoustically by thedistance between their centers, represented by the broken lines shown inFIG. 9. Conductors 63 and 64 may be routed downwardly between the postsin a known fashion, if desired.

An important design parameter for the purposes of the instant inventionis that the hydrophone transducer 41 be configured to have a resonantfrequency which is higher than the operational frequency of theensonifying projector transducers 43. This is because a phase shiftoccurs within a hydrophone transducer for operational frequencies in theregion of electrical resonance. Since a phase detection system is to beused as an important component in the signal processing channel of thesystem of the invention, such internal phase alterations within thehydrophone itself are to be avoided. Configuring the transducer toresonate well above the operational frequency of the system effectivelyprevents these phase alterations from occurring.

Before proceeding to the description of the electronic circuitry ofApplicants invention, some particular features of the novel informationreadout arrangement will be explained. In murky waters or afternightfall swimmer-diver personnel have no useful visual information.This lack of visual contact is especially acute where an element ofsecrecy is desired, such as in Naval operations, and the use of lightingis precluded. Under such conditions underwater swimmerdiver personnelfrequently become disoriented and experience difficulties in navigating.The visual readout of the invention provides a choice between the visualpresentation of the ranging system, the normal visual perception of thesurroundings, and a composite presentation of the two presentedsuperimposed one on the other.

Referring to FIG. 10, the viewing mask assembly 25 of the invention isshown as it is worn by swimmer-diver 21. A conventionally constructedface mask 65 has an optical unit 66 mounted on the upper wall 67thereof. Optical unit 66 is joined to the battery and electronicspackage by a fibre optic image transmission cable 26 (see also FIG. 1).Face mask 65 is shaped at the side portion 68 to receive the opticalunit 66 when it is pivoted to one side, so as to permit an unobstructedvision through viewing plate 61. When in viewing position, the opticalunit 66 is positioned over one eye of diver 21 and lens 71 is alignedtherewith.

It should be made clear that, although the invention is described as amonocular arrangement, the invention may be configured as a binocularviewing device. In such instances the optical viewing unit would providefor both eyes to view the presentation and may pivot vertically to aposition above or foreward of upper wall 67 of viewing mask 25.

Referring to FIG. 11, the details of construction of the optical unit 66are shown in greater detail. The optics are contained in a housing 72which supports lens 71 on the front surface thereof. A rubber, or otherflexible material, bellows 73 extends from the rear surface of housing72 to resiliently abut viewing plate 69 and provide a glare free viewingpath from the divers eye, shown schematically at 74, through housing 72.

Within housing 72 is an image forming bundle 75 which terminates in animage display surface 76. A lens 77 relays the image to prism 78 in sucha fashion as to appear to be at a distance of approximately 15 to 20meters. Prism 78 has a lower, semi-reflecting surface 79 which permitsthe visual superposition of the display image from surface 76 and theview of the surrounding transmitted via lens 71.

It is sometimes desirable to exclude the view from lens 71 to permitexamination of the sonar image displayed on surface 76 alone. For thispurpose, a reflector 81 is pivotably supported below prism 78. Reflector81 may be moved into contact with semireflecting surface 79 by pusherarm 82. Pusher arm 82 is actuated by suitable means, not shown, on theexterior of housing 72, or by solenoid means, not shown, located withinhousing 72. Ordinarily, the viewing of the sonar display alone isperformed for short periods, and, accordingly, reflector 81 is springbiased to the position shown. Should longer periods of exclusively sonarreadout dis play be desired, suitable catch means, not shown, may beemployed to hold reflector 8i against prism 78.

The circuitry, shown in FIG. 12 in block diagram form, provides for theoperation of the invention. A clock circuit 83 produces a series ofpredetermined pulses which are used to producethe timed and synchronousoperation of the individual circuit arrangements comprising the system.The output signal pulses from clock 83 are connected by suitablecircuitry to a ring counter-programmer circuit 841, a staircasegenerator 85, a sawtooth generator 86, and a gated oscillator 87.

Staircase generator 85 is also connected to bit ring counter-programmer84 to receive an output therefrom. Staircase generator 85 is configuredto produce a twenty step staircase voltage waveform in response to thesignals supplied it from clock 83 and ring counterprogrammmer 84. Clock83, staircase generator 85, sawtooth generator 86, and gated oscillator87 comprises a timing means which controls the timed relationships ofthe other components of the system.

The ring counter-programmer 84), to be more fully described herein, isconnected to multiplexer circuit 88 and multiplexer and power amplifercircuit 89. The output of gated oscillator circuit 87 is also connectedto multiplexer and power amplifier circuit 89. Multiplexer and poweramplifer circuit 89 is connected so as to provide a timed actuation ofparticular transducer in projector array 39. Multiplexer 88 provides asignal transfer path from the hydrophone array portion 38 of transducerassembly 37 to left and right preamplifers 91 and 92, respectively. Thefunction and construction of multiplexer 88 and multiplexer and poweramplifer 89 will be more completely described herein.

Preamplifiers 9i and 92 are connected to filters 93 and 94,respectively. As indicated, filters 93 and 94 are designed to pass aselect band of frequencies and reject, i.e., block the passage of,frequencies above and below said select band. Filters 93 and 94 areelectrically identical and, accordingly, limit the frequency content ofthe two channels to the same spectrum. A limiter 95' is connected tofilter 93 to effectively remove the amplitude variations from the outputthereof.

A similar limiter 9e and a time varied gain amplifier 97 are connectedto filter 94. The output of filter 94 supplies the highlightinformation, as will be more fully explained herein, and this accountsto its output being connected to TVG amplifier 97 prior to having theamplitude variations removed.

Limiter 96 is connected in circuit with a bistable delay 98 so as toapply its output thereto. Bistable delay 98, as its name implies, delaysin time the transmission of the output of limiter 96 for one of twofixed time intervals. The time interval that is used is determined bythe output of twenty bit ring counter 84 which is connected to bistabledelay 98 via appropriate circuit connection means.

A phase detector 99 of a novel construction is connected to limiter 95so as to receive the output therefrom, and is connected to bistabledelay 98 so as to receive the time delayed output of limiter 96therefrom. One output of phase detector 99 is a function of thedifference in arrival time of the two input signals, and is connected tothe input of summing amplifier 18!. Preamplifiers 9H and 92, filters 93and 94, limiters 95 and 96, bistable delay 98 and phase detector 99comprise the dual channel receiver means of the invention.

Summingamplifier 101 is also connected to staircase generator to receivethe 20 step waveform therefrom. Amplifier 101 combines these two signalsinto a composite sum signal of an amplitude of a predetermined valuecorresponding to the bearing of the center of reflection. Amplifier 101iis connected to the x axis input circuit 102 of a visual readout 1103.

Phase detector 99 produces a second output signal which indicateswhether or not the arrival times of the input signals thereto werewithin a predetermined time interval. A transmission gate 104 isconnected to phase detector 99 so as to receive this second signaltherefrom. This second signal, as will be readily apparent to thosefamiliar with electronic ranging circuitry of the type described herein,determines if the signals originally impinged the hydrophone array 38from a predetermined angular sector. This angular sector is chosen so asto exclude returns from composite patterns produced by adjacentprojector transducer and hydrophone transducer pairs. Transmission gateMM controls the highlight display.

As previously noted, the highlight signals are derived from theunlimited output of filter 94 which is connected to time varied gainamplifer 97. The gain of amplifier 97 is controlled by the output ofsawtooth generator 86 which is connected to a slope modificationpreamplifier ll05. The slope of the sawtooth is adjusted, in the wellunderstood manner, to compensate the gain for signal loss due toattenuation by the medium over the expected range of the system. Slopepreamplifier W5 is connected to time varied gain amplifier 97 to controlthe time-gain function thereof.

The amplitude variations in the output of TVG amplifier 97 are detectedby detector 106 to which it is connected. Detector 106 is effectivelyelectrically connected to a low pass filter 107. Filter B07 removes thehigh frequency amplitude variations from the detected video signal priorto display.

Filter W7 is connected to the previously mentioned transmission gate MM.Transmission gate 11943 is connected in circuit with Z axis inputcircuit 1108 for dis play of target highlights as intensity variations.Gate 104 prevents a display when the signal is from a sector outside thepredetermined acceptance angle as explained in description of phasedetector 99, supra, and to be more completely described herein.

The remaining input to visual readout H03 comes from sawtooth generator86. Sawtooth generator 86 is connected to Y axis input circuit 189 so asto provide a time varying signal to provide a range generating sweep onwhich the highlight and bearing information are displayed. Asillustrated schematically, X axis input circuit 192, Y axis inputcircuit 109, and Z axis input circuit are all effectively connected tosupply cathode ray tube 111 with operational signals.

As previously noted, the cathode ray tube 111 is physically locatedwithin battery and electronics package 24 located on the life supportsystem 23 (FIG. 1). In some developmental units cathode ray tube 111 hasbeen located on the viewing mask 25 and may be so mounted in theinvention, if desired. However, such an arrangement requires highvoltage conductors to lead externally around the head of swimmer-diver21, a systern with obvious dangers to operating personnel.

it is difficult at the present state-of-the-art to obtain a cathode raytube to meet the requirements of compactness, persistency, andbrightness imposed by the operational parameters in which the system isto be used. For example, in some waters the visibility is low despite arelatively high light level. In such circumstances, the brightness ofthe video display produced by cathode tube 111 must exceed that of theambient light to be seen by diver 21. As pointed out above, the presentstate-of-the-art cathode ray tube of dimensions sufficiently small tomount in battery and electronics package 24 and of the persistency to beused in sonar applications requires a light intensifier 1 12 to beplaced between cathode ray tube 111 and fibre optics input bundle 113.

When performing duties under water, the personnel using the sonar arequite occupied, and duties that are not essential are often neglected.It is for this reason the device of the invention may be equipped with abrightness adjustment circuit to free the diver from making controladjustments and to automatically keep the display at an optimumbrightness.

The brightness control circuit comprises a light collector 114. Theambient light falling on light collector 114, shown as a positive lens,is directed to suitable photoelectric transducer means 115. An automaticgain control amplifier 116 is electrically connected to photoelectrictransducer 115. The output of photoelectric transducer 115 causes thegain of A.G.C. amplifier 116 to be adjusted to attain a predeterminedvalue with respect thereto. AGC amplifier 116 is connected to lightintensifier 112 to control the optical gain thereof.

Should a suitably dimensioned cathode ray tube with sufficientbrightness become available, or should operation only in low lightlevels be expected, the circuit arrangement of FIG. 13 could be employedfor an automatic brightness controlled readout arrangement. Visualreadout. 1113 employs such a bright cathode ray tube 117 coupleddirectly to fibre optic bundle 113 without an intermediate lightintensifier. The light sensing arrangement of light collector 114 andphotoelectric transducer 115 function as in the arrangement in FIG. 12.Automatic gain control amplifier 116 is connected to Z axis inputcircuit 108 to vary the gain thereofand to effectively alter thebrightness of the display in accordance with the ambient light level. Insuch an arrangement X axis input circuit 102 and Y axis input circuit109 function as in the circuit of FIG. 12.

As will be obvious to persons versed in the electroacoustic rangingarts, some of the circuits identified as blocks in FIG. 12 arethemselves rather complex circuit arrangements, but are so well known asnot to require further description. Similarly it should be recognizedthat a variety ofcircuits are well known which will perform the designfunctions satisfactorily in the system of the invention. Accordingly,the selection as between different ones of these well known prior artcircuit arrangements is regarded as a matter of design choice to aproficient artisan.

However, certain ones of the circuit blocks, to be more fully identifiedand described herein, are departures from standard prior art circuitry.In certain ones thereof the departures from known circuit arrange mentsare for the purpose of optimizing the circuit arrangement for use in thesystem of the invention. In other circuits, innovations are presentedherein which are meritorious advances in the electroacoustic circuitryarts per se. These circuits, although capable of independent andseparate application, are described with sufficient detail to enable askilled artisan to make and use the acoustic ranging system of theinvention.

Referring to FIG. 14, projector multiplexer-power amplifier circuit 89is shown in block diagram form. Each projector transducer 43 is drivenby a power amplifier 118. Each of the power amplifiers 118 are identicaland raise the power level of the pulse of acoustic energy pulse suppliedby gated oscillator $7, a unijunction oscillator in the developmentalmodel of the invention, to a level sufficient to ensonify the desiredprojection pattern. Each of power amplifiers 118 is fed the input fromgated oscillator 87 by a transmission gage 119. Transmission gates 119are energized sequentially by twenty bit counter 84, to be described ingreater detail herein. The reason for having an individual poweramplifier 118 for each projector channel is based on the reliability ofgates 119 when repeatedly switching high level acoustic power pulses. Ifreliable switching circuitry of compact dimensions could be developed, amore direct circuit arrangement would be possible.

FIG. 15 shows such an alternative arrangement. As is shown therein,amplifiers 118 have been replaced with a single amplifier 121.Similarly, gates 119 of FIG. 14 have been replaced by high power gates122. The two circuits function in the same fashion, and, for thepurposes of the invention, may be used interchangeably.

In both of FIGS. 14 and 15, only four channels are shown for purposes ofillustration, but it should be understood that each circuit has tenchannels in the preferred embodiment.

FIG. 16 illustrates the multiplex circuit 88 in a more complete, butstill diagrammatic, fashion. As previously explained, each hydrophonetransducer 41 has a right and a left array. Each of the right arrays areconnected, via conductor 63 to a right received signal gate 123.Similarly, each hydrophone has its left array connected, via conductor64, to a left received signal gate 124. Each hydrophone transducer 41has its associated right received signal gate 123 and its left receivedsignal gate 124 have their trigger inputs connected in parallel to betriggered simultaneously by the ring counterprogrammer circuit 84. Theeleven individual channels in the receiving channel each comprise ahydrophone transducer 41, a right received signal gate 123, and a leftreceived channel gate 124. The eleven channels are triggered in apredetermined sequence by the ring counter circuit 84, which serves as aprogrammer for the combined operation of the hydrophone transducers 41and the projector transducers 43. The terms left and right are used inthis discussion are understood as being only mutually exclusive, and, insome orientations, may

actually correspond to other interrelations such as up and down.

The construction of the ring counter-programmer circuit 84 isdiagrammatically illustrated in FIG. 17. The principal component in thecircuit is a twenty bit ring counter 125. The counter functions in aconven tional manner for circuits of its kind, i.e., conduction advancesone stage for each pulse input received from clock circuit 83. The ringcounter 125 is illustrated foreshortened with only nine of its twentystages shown. Each of the stages are numbered to correspond to thesequence in which it is activated.

The output of each stage of ring counter 125 are illustrated as twoterminals so as to agree with the illustration of circuit 84 in FIG. 12and to simplify explanation thereof, but, in fact, the outputs may betaken from a common point. As illustrated, one set of outputs areultimately associated with the eleven receiving hydrophone channels andthese outputs are labeled 11,, H etc. The other set of outputs areultimately used to trigger the ten gates 119 or 122 in multiplexer andpower amplifier circuit 89, and are labeled P P etc. It will be notedthat the first and last stages of ring counter 125 are used to triggerthe associated hydrophone gate pairs directly. The remaining stages areprocessed by a plurality of identical or gates 126. There are nine orgates 126 for the hydrophone channels and they accept inputs fromadjacent stages of ring counter 125 starting with the second and thirdstates. Ten similar or gates 126 receive inputs from adjacent stages ofring counter 125, starting with stages one and two, and are used totrigger the gates 119 or 122 in the projector channels.

A monostable multivibrator 127 is triggered by the last, i.e., twentiethstage. The output of this stage is connected to, and provides for thereset pulse for, staircase generator 86, as previously noted inconnection with FIG. 12.

It may be seen from inspection of FIG. 17 that, upon receipt of thefirst clock pulse, stage one of counter 125 is energized. This energizesthe first hydrophone channel and the first projector channel. A secondclock pulse energizes the second stage of counter 125, and, accordingly,triggers the second hydrophone and the first projector channels. Thethird clock pulse energizes the third stage of ring counter 125, andtriggers the second hydrophone channel and the second projector channel.Subsequent clock pulses trigger succeeding stages of counter 125 intoconduction to advance the triggering of subsequent projector andreceiver channels that each one, except for the first and last receiverchannels, is used twice in succession. This sequential switching actiontogether with the relative positioning of the transducers as shown atFIGS. 3, 4 and 5, and discussed above, produce the radiation andreception patterns 17 and 48 shown in FIG. 7 and described above.

An output is taken from alternate stages of ring counter 1125 startingwitn the first stage. These outputs, labeled x in FIG. 17, are connectedas inputs to 10 input or gate 128. The output from or is connected tobistable delay 89, as will be presently described, for the purpose ofsynchronous triggering thereof.

The construction of the bistable delay circuit 98 and the cooperatingphase detector circuit 99 is explained with reference to FIG. 18.Because circuits 98 and 99,

like most circuits in modern electronic systems, employ micro orintegrated circuits the block diagram like illustration is actually thewiring diagram of the circuit. The particular circuit configuration ofthe electrical circuitry encompassed within the blocks is illustratedseparately and the appropriate figures will be referred to fromtime-to-time in the course of the following description. In practice,however, these circuits are commercially available units and areconnected in circuit as if they were single active elements.

When employed by itself as a receiver, a given hydrophone transducer 411has an acoustic axis centered between the axis of the two arrays ofposts. However, as discussed above, each hydrophone transducer 41 ispaired with two projector transducers 43 spaced on either side thereof.For one ping-listen cycle the hydrophone is used in conjunction with theprojector transducer 43 on one side thereof, and on the next pinglistencycle it is used in conjunction with the projector transducer 43 on theopposite side thereof. As a result of this alternate use to establish asector scanning arrangement, the acoustic axis of the composite patternwill be shifted to one side of the normal axis of hydrophone transducer41. In the instant invention this shift corresponds to an angular shiftof i2B/6". As a result of this, a difference in time of arrival, termedA t, occurs for an echo return on the axis of the composite beam whenone projector transducer 43 is used as compared to a return of the samerange and relative bearing when the other projector transducer 43 isused.

Assuming the beamwidth of the composite pattern for the device of theinvention is approximately 2 at the half power points, the phasedetector circuit 99 is designed to determine the incident angle ofwavefronts received within this composite pattern beamwidth an accuracyof 0.25". Phase detector circuit 99 also prohibits the amplitudeinformation of wavefronts received from directions outside of thedesired angular response beam from reaching the cathode-ray tube display103. The system is, in such a hypothetical system, only responsive toechoes having bearing angles of i1. A bearing of 1 relative to theacoustic axis of the hydrophones corresponds to an arrival timedifference of 192 nanoseconds (ns) in the system of the example. Anaccuracy of 025 corresponds to detecting an arrival time difference of48 ns.

A wavefront incident 1 to the left of the acoustic axis was assigned att 0 for proper display orientation. Then an axis return in one patterncorresponds to a At of 192 ns and for the adjacent composite pattern toa At of 384 ns. Thus the signal output of the right hydrophone willalways lag the signal from the left. The bistable delay 5% mentionedpreviously and located in the right channel (FIG. 12), must add a delayT when the acoustic axis of the composite pattern is displayed --0.75,and a delay T when it is displayed 10.75". At for 0.75 is 144 ns;therefore, for one complex pattern this delay corresponds to 192 ns 144ns, or 48 ns, and for the adjacent pattern the delay corresponds to 192ns ns, or 336 ns.

Bistable delay circuit 89 comprises a monostable multivibrator 129 whichis triggered by the amplitude limited waveform, shown at A in H6. 19,from right channel limiter 96. This waveform is a square wave of theoperating frequency. As shown at FIG. 20, monostable multivibrator 129comprises a five transistor, seven diode circuit. A variety ofintegrated circuits three of the integrated circuit. The pulse width ofmonostable multivibrator 129 may be controlled with respect to designedvalue by applying a voltage at pin 3, as is done in this instance, andby connecting a capacitor between pins three and four. As may be seenfrom the circuit configuration of FIG. 211, an external capacitorbetween pins three and four shunts capacitor 132 to alter the pulsewidth. A change in voltage at pin 3 alters the voltage drop acrossresistor 133 to produce a similar alteration in pulse width. In thedevice of the invention, capacitor 134) causes monostable rnultivibrator129, abbreviated MSMV 129, to produce the 336 ns delay and the voltageoutput ofor gate 128 is regulated to produce the 48 ns delay. Thefrequency of the switching of delays is very slow since it is at thepinglisten cycle rate, in comparision to the other pulses, which are atthe operating frequency rate.

Phase detector 99 comprises 'monostable multivibrators, abbreviatedMSMV, 135, 136, 137, 138, and 139. Each of these circuits is identicalwith MSMV 129 with the exception of external connections. Quadruple NANDgate 1 11, power supply 142, and integrate and hold output circuit 143are connected in circuit with the aforementioned MSMV circuits as shownin FIG. 18. Waveforms illustrated in FIG. 19, and circuit detailsillustrated in FIGS. 21 and 22 will be referred to from time-to-time tomore clearly explain the operational details of phase detector 99,illustrated at FIG. 18.

Power supply 1 12 comprises a regulating transistor 144 which is biasedto regulate the output voltage to a predetermined value with respect toa reference potential established by zener diode 145. The regulatedvoltage is distributed by the illustrated circuitry to all componentstages of bistable delay 39 and phase detector 99.

MSMV 135 is connected to receive the delayed output of bistable delay39, waveform B. The pulse width of waveform B establishes the desireddelay in accordance with the value of capacitor 134 and the voltageapplied via diode 131 as discussed previously. The negative going edgeof waveform B triggers MSMV 135 to produce a positive pulse output shownat waveform C, and having a pulse width regulated by capacitor 1416. Thepulse width of waveform C is chosen to be of a time durationcorresponding to twice the desired angular resolving power as discussedabove.

MSMV 1311 is connected to receive the output of limiter 9E, waveform I),and produces a positive pulsed waveform E in response thereto. MSMV 136is configured to be electrically identical to MSMV 135.

The outputs of MSMVs 135 and 136, waveforms C and E, respectively, arefed to quadruple NAND" gate 141. As shown at FIG. 21, quadruple gate 141comprises four NAND gates 1417, M11, M9, and 151. Each of the gates isconfigured as shown at FIG. 22. A variety of circuits may be used forquadruple NAND gate 1411. The unit marketed by Signetics Corporation ofSunnyvale, California, under the designation SE48OJ has provensatisfactory, and is cited as an example of a type which may be usedsuccessfully for the purposes of the invention.

The individual circuit arrangement shown at FIG. 22 reveals that thecircuit comprises a transistor 152 with dual emitters. When an input ofthe proper characteristics appears on each of the two emitterssimultaneously, transistor 152 conducts. Transistor 152 and associatedcircuitry form an AND gate 153. The output of AND gate 153 is invertedby the action of transistors 154 and 155 to produce the NAND," or NOTAND, logic function. a

In phase detector 98, FIG. 18, quadruple gate 14-1 is wired such thatNAND gate 151 has its output connected to one input of NAND gate 149.The other imput of gate 149 is connected to a fixed voltage source suchthat gate 149 merely inverts the output of NAND gate 151 to produce anAND" function of the inputs thereof. This output, waveform F, isconnected to integrate and hold circuit 143 and to MSMV 137.

MSMV 137, which has its pulse width unmodified by external capacitors,produces a spike pulse output, waveform G.

As previously noted, the waveform F is also applied to integrate andhold circuit 143. The pulse width of waveform F has been processed, asnoted above, such that it is a function of the difference in arrivaltime of the same cycle of returned echo to the left and right arrays ofthe hydrophone transducer 41 then in use. This time difference, aspreviously explained, is a function of the bearing within a compositebeam pattern of the center of reflection. Integrate and hold circuit 143charges capacitor 156 to a value dependent upon the duration of thepulse of waveform F.

The output of integrate and hold circuit 143, waveform H, is connectedto summing amplifier 101 (FIG. 12) where it is combined with the outputof staircase generator to position the beam in a horizontal direction.The beam position is held until the next cycle of the returned echo orreverberation signal when the integrate and hold circuit 1413 againindicates the center of reflection.

Integrate and hold circuit 143 is reset by transistor 157 which, whenenergized, discharges hold capacitor 156.

Transistor 157 is triggered by a spike pulse output of MSMV 138, shownat J in FIG. 19. MSMV 133 is, in turn, triggered by the delayed outputof bistable delay 129, waveform B.

The output of MSMV 135, waveform C, and the output of MSMV 137, waveformC, are connected to qua druple NAND gate 141 where they are combined inNAND gate 148. The output of NAND gate M8, wave form K.

MSMV 139 is connected to receive the output of NAND gate 148 and betriggered thereby. The output pulse width of MSMV 139, waveform L, isdetermined by capacitor 158, and is chosen to permit gate 104 (FIG. 12)to pass the amplitude information contained in the echo return so as tobe displayed by visual readout 103. Should the echo return impinge froma direc tion outside the predetermined angular bandwidth, there will beno output from NAND gate 148 and transmission gate 104 will blockamplitude information from being displayed.

NAND gate 147, although contained in integrated quadruple NAND gate 141,is not used in the circuitry of the invention.

PREFERRED MODE OF OPERATION The operation of the device of the instantinvention is considered straightforward, and differs from other acousticranging and detection systems only in its compactness and specialenvironmental aspects. Accordingly, this description will deal primarilyto the operational manipulation performed by a swimmer-user of thesystem. FIGS. 4, 10, and 11 illustrate the controls normally used inoperating the system.

The swimmer enters the water with the system turned off and the opticalunit 66 in its inoperative position, shown by broken lines in FIG. 10.Upon reaching an area where his vision is obscurred, the system isenergized by pressing control switch 34. Optical unit 66 is positionedbefore the eye, or eyes in the event a binocular presentation isemployed, and reflector 84 adjusted to provide the presentation desired.Control ring 35 is then adjusted to set the slope of the slopepreamplifier 105 to cause time varied gain circuit 97 to fill thepresentation to the optimum range. Practical experience has shown atwenty meter range for a swimmer height of three and one half metersfrom the bottom is optimum. Control ring may effect a continuousadjustment or select one of a plurality of set TVG slopes for differentbottom conditions.

The swimmer-diver 21 traverses the area with the control unit 27 eitherhand held, as illustrated in FIG. 1, or clipped to his person. Headmounting may be used if desired, but has proven somewhat troublesome asswimming and performing underwater tasks causes head movements resultingin blurred images and optical distraction. Perhaps becauseswimming-diving personnel have grown accustomed to hand held electriclights, or some other psychological reason, the hand held operationseems preferred.

The acoustic energy is projected from, and returned to, control unit 27which, in addition to supporting the electroacoustic energy converters,provides a mounting for the electrical controls and houses the ringcounterprogrammer 84, receive-multiplex circuit 88, multiplex-poweramplifier 89, as well as some component circuits of the dual channelreceiver means. The signal from hydrophone means M in use is processed,amplitude and phase detected as previously explained in connection withFIG. 12.

1f the signal is transmitted by gate 104, i.e., if the return is withinpredetermined limits, a visual light image is produced by visual readout103. The display produced by visual readout 103, which is physicallylocated in battery and electronics package 24, is transferred via fibreoptical bundle '75, to optical unit 66.

If it is desired to study the sonar image in detail, reflector 81 (H0.11) is positioned against prism 78. This may be accomplished either witha manual control of pusher arm 84! or electrically by use of switch 32to control a solenoid, not shown, mounted within optical unit 21.

Switch 33 may be connected to gate circuit 104 to cause interruption ofthe sonar display. In such an operation swimmer-diver Z1 sees only thevisually preceived details of his environment.

The phase-detector action, previously described, presents an improvedimage resolution not heretofore obtainable. This presentation, togetherwith the compact scanning arrangement made possible by theaforedescribed construction and circuitry details, provides an improvedsonar system for swimmer-diver use. The advantages offered by thissystem ove the proper art systems are so marked as to constitute anunobvious advance in the art.

Obviously, other embodiments and modifications of the subject inventionwill readily come to the mind of one skilled in the art having thebenefit of the teachings presented in the foregoing description and thedrawings. it is, therefore, to be understood that this invention is notto be limited thereto and that said modifications and embodiments areintended to be included within the scope of the appended claims.

What is claimed is:

1. A portable sonar system comprising in combination:

a plurality of angularly oriented linear transducer means for convertingelectrical energy supplied thereto into acoustical energy;

a plurality of angularly oriented hydrophorie means adjacent to saidplurality of angularly oriented linear transducer means for convertingacoustic energy impinging thereon into electrical signals, each of saidhydrophone means comprising left and right linear arrays of hydrophoneelements and having a predetermined angular orientation with respect toindividual ones of said transducer means;

control unit means effectively attached to said plurality of transducermeans and to said plurality of hydrophone means, so as to providecooperative relationship therebetween and configured so as to facilitatemanual positioning thereof for directing the investigative beam patternof said sonar system;

a receive-multiplex circuit means effectively electrically connected tosaid plurality of hydrophone means for selectively transmitting signalsfrom a single one thereof into left and right channels corresponding tosaid left and right arrays of hydrophone elements;

multiplex-power amplifier circuit means effectively connected to saidplurality of transducer means for selectively applying a pulse ofelectrical energy to one thereof;

ring counter-programmer means effectively connected to saidreceive-multiplex circuit means and effectively connected to saidmultiplex-power amplifier circuit means for the actuation thereof in apredetermined programmed sequence;

dual channel receiver means effectively connected to said receivemultiplex circuit means for processing the signals from the left andright channels thereof;

to the phase difference between the left and rightchannel signalsthereof for producing a first output signal which is a function of thephase difference of said left and right signals and a second outputsigna! if the phase of said left and right signals is withinpredetermined limits;

signal transmission gate circuit means effectively connected to saidamplitude detection circuit means to receive the output signal therefromand effectively connected to said phase detection circuit means toreceive said second output signal therefrom for effecting the passage ofsaid first output signal from said amplitude detection circuit when saidsecond output signal from said phase detection circuit means correspondsto a phase relationship within said predetermined limits;

visual readout means effectively connected to said signal transmissiongate for displaying the signals passed thereby as light intensityvariations and effectively connected to said phase detector circuitmeans to receive said first signal therefrom for positioning saiddisplayed light intensity signals in response thereto;

timing circuit means effectively connected to saidring-counter-programmer circuit means, said multiplex-power amplifiercircuit means, and said visual readout means for supplying electricalsignals corresponding to predetermined time functions thereto; and

optical means operatively associated with said visual readout means fortransmitting the light output thereof to a position remote therefrom forvisual readout thereof.

2. A portable sonar system according to claim 1 in which said left andright arrays of hydrophone elements spatially overlap such thatindividual elements of one array are placed between adjacent individualelements of the other array.

3. A portable sonar system according to claim 1 in which said dualchannel receiver means includes, in one channel thereof, a bistabledelay circuit means for delaying pulses passed therethrough for one oftwo predetermined time intervals in response to control signals appliedthereto.

4. A portable sonar system according to claim 3 in which said ringcounter'programmer means further comprises in combination:

ring counter circuit means electrically connected to said timing circuitmeans for receipt of signals therefrom, and having outputs from thefirst and last stages thereof electrically connected to said receivemultiplex circuit means;

a first series of binary input or gates electrically connected tosuccessive stages of said ring counter circuit means such thatsuccessive ones of said or gates receive inputs from successive,nonoverlapping pairs of the stages of said ring counter circuit meansstarting with the first stage thereof, the outputs of said first seriesof or" gates being connected to said multiplex-power amplifier circuitmeans;

a second series of binary input or gates electrically connected tosuccessive stages of said ring counter circuit means such thatsuccessive ones of said second series ofor" gates receive inputs fromsuccessive, nonoverlapping pairs of the stages of said ring countercircuit means starting with the second stage thereof, and having outputstherefrom connected to said receive-multiplex circuit means; and

multiinput or circuit means connected so as to receive inputs from theoutputs from alternate ones of the stages of said ring counter circuitmeans starting with said first stage thereof and having its outputconnected to said bistable delay means.

5. A portable sonar system according to clam l in which said phasedetection circuit means further comprises in combination:

a pulse generator circuit means for generating a pulse having a widthwhich is a function of the difference in time of arrival of acousticenergy which is impinging said left and right hydrophone element arrays;and

integrate and hold circuit means electrically connected to said pulsegenerator circuit means for generating and holding a voltage which is afunc tion of the length of the pulse generated thereby.

6. A portable sonar system according to claim 5 in which said phasedetection circuit means further comprises in combination:

logic circuit means electrically connected to said pulse generatorcircuit means for comparing said pulse width to a predetermined timeduration; and

second pulse generator circuit means electrically connected to saidlogic circuit so as to receive the output thereof for generating acontrol pulse in response thereto.

7. A portable sonar system according to claim 5 in which said phasedetection circuit means further comprises in combination, a triggerpulse generator means connected in electrical circuit so as to receivethe output of one channel of aforesaid dual channel receiver means forresetting said integrate and hold circuit means.

8. A portable sonar system according to claim 1 in which said visualreadout means further comprises in combination:

cathode ray tube means electrically connected to said signaltransmission gate circuit means for converting electrical signalsreceived therefrom to visual signals; and

light intensifier means fixedly positioned so as to be effectivelyoperatively associated with said cathode ray tube means for increasingthe light intensity of the output thereof prior to transmission toaforesaid optical means.

9. A portable sonar system according to claim 8 in which said visualreadout means further comprises in combination:

gain control means electrically connected to said light intensifiermeans for control of the light intensity of the output thereof; and

light sensing means positioned to be illuminated by the ambient lightsurrounding said sonar system and electrically connected to said gaincontrol for the regulation thereof in response to the level of ambientillumination.

10. A portable sonar system according to claim 9 in which said visualreadout means further comprises an optical light collector means fixedlypositioned to collect the ambient light in the region of said sonarsystem and to transmit said ambient light to said light sensing meansfor the electrical control thereof.

l= =l l-

1. A portable sonar system comprising in combination: a plurality ofangularly oriented linear transducer means for converting electricalenergy supplied thereto into acoustical energy; a plurality of angularlyoriented hydrophone means adjacent to said plurality of angularlyoriented linear transducer means for converting acoustic energyimpinging thereon into electrical signals, each of said hydrophone meanscomprising left and right linear arrays of hydrophone elements andhaving a predetermined angular orientation with respect to individualones of said transducer means; control unit means effectively attachedto said plurality of transducer means and to said plurality ofhydrophone means, so as to provide cooperative relationship therebetweenand configured so as to facilitate manual positioning thereof fordirecting the investigative beam pattern of said sonar system; areceive-multiplex circuit means effectively electrically connected tosaid plurality of hydrophone means for selectively transmitting signalsfrom a single one thereof into left and right channels corresponding tosaid left and right arrays of hydrophone elements; multiplex-poweramplifier circuit means effectively connected to said plurality oftransducer means for selectively applying a pulse of electrical energyto one thereof; ring counter-programmer means effectively connected tosaid receive-multiplex circuit means and effectively connected to saidmultiplex-power amplifier circuit means for the actuation thereof in apredetermined programmed sequence; dual channel receiver meanseffectively connected to said receive multiplex circuit means forprocessing the signals from the left and right channels thereof;amplitude detection circuit means effectively connected to one channelof said dual channel receiver means for detecting the amplitudevariations in the signals processed thereby and for producing an outputsignal which is a direct function thereof; phase detection circuit meanseffectively connected to said dual channel receiver means and responsiveto the phase difference between the left and right channel signalsthereof for producing a first output signal which is a function of thephase difference of said left and right signals and a second outputsignal if the phase of said left and right signals is withinpredetermined limits; signal transmission gate circuit means effectivelyconnected to said amplitude detection circuit means to receive theoutput signal therefrom and effectively connected to said phasedetection circuit means to receive said second output signal therefromfor effecting the passage of said first output signal from saidamplitUde detection circuit when said second output signal from saidphase detection circuit means corresponds to a phase relationship withinsaid predetermined limits; visual readout means effectively connected tosaid signal transmission gate for displaying the signals passed therebyas light intensity variations and effectively connected to said phasedetector circuit means to receive said first signal therefrom forpositioning said displayed light intensity signals in response thereto;timing circuit means effectively connected to saidring-counterprogrammer circuit means, said multiplex-power amplifiercircuit means, and said visual readout means for supplying electricalsignals corresponding to predetermined time functions thereto; andoptical means operatively associated with said visual readout means fortransmitting the light output thereof to a position remote therefrom forvisual readout thereof.
 2. A portable sonar system according to claim 1in which said left and right arrays of hydrophone elements spatiallyoverlap such that individual elements of one array are placed betweenadjacent individual elements of the other array.
 3. A portable sonarsystem according to claim 1 in which said dual channel receiver meansincludes, in one channel thereof, a bistable delay circuit means fordelaying pulses passed therethrough for one of two predetermined timeintervals in response to control signals applied thereto.
 4. A portablesonar system according to claim 3 in which said ring counter-programmermeans further comprises in combination: ring counter circuit meanselectrically connected to said timing circuit means for receipt ofsignals therefrom, and having outputs from the first and last stagesthereof electrically connected to said receive multiplex circuit means;a first series of binary input ''''or'''' gates electrically connectedto successive stages of said ring counter circuit means such thatsuccessive ones of said ''''or'''' gates receive inputs from successive,nonoverlapping pairs of the stages of said ring counter circuit meansstarting with the first stage thereof, the outputs of said first seriesof ''''or'''' gates being connected to said multiplex-power amplifiercircuit means; a second series of binary input ''''or'''' gateselectrically connected to successive stages of said ring counter circuitmeans such that successive ones of said second series of ''''or''''gates receive inputs from successive, nonoverlapping pairs of the stagesof said ring counter circuit means starting with the second stagethereof, and having outputs therefrom connected to saidreceive-multiplex circuit means; and multiinput ''''or'''' circuit meansconnected so as to receive inputs from the outputs from alternate onesof the stages of said ring counter circuit means starting with saidfirst stage thereof and having its output connected to said bistabledelay means.
 5. A portable sonar system according to clam 1 in whichsaid phase detection circuit means further comprises in combination: apulse generator circuit means for generating a pulse having a widthwhich is a function of the difference in time of arrival of acousticenergy which is impinging said left and right hydrophone element arrays;and integrate and hold circuit means electrically connected to saidpulse generator circuit means for generating and holding a voltage whichis a function of the length of the pulse generated thereby.
 6. Aportable sonar system according to claim 5 in which said phase detectioncircuit means further comprises in combination: logic circuit meanselectrically connected to said pulse generator circuit means forcomparing said pulse width to a predetermined time duration; and secondpulse generator circuit means electrically connected to said logiccircuit so as to receive the output thereof for generating a controlpulse in response thereto.
 7. A portable sonar system according to claim5 in which said phAse detection circuit means further comprises incombination, a trigger pulse generator means connected in electricalcircuit so as to receive the output of one channel of aforesaid dualchannel receiver means for resetting said integrate and hold circuitmeans.
 8. A portable sonar system according to claim 1 in which saidvisual readout means further comprises in combination: cathode ray tubemeans electrically connected to said signal transmission gate circuitmeans for converting electrical signals received therefrom to visualsignals; and light intensifier means fixedly positioned so as to beeffectively operatively associated with said cathode ray tube means forincreasing the light intensity of the output thereof prior totransmission to aforesaid optical means.
 9. A portable sonar systemaccording to claim 8 in which said visual readout means furthercomprises in combination: gain control means electrically connected tosaid light intensifier means for control of the light intensity of theoutput thereof; and light sensing means positioned to be illuminated bythe ambient light surrounding said sonar system and electricallyconnected to said gain control for the regulation thereof in response tothe level of ambient illumination.
 10. A portable sonar system accordingto claim 9 in which said visual readout means further comprises anoptical light collector means fixedly positioned to collect the ambientlight in the region of said sonar system and to transmit said ambientlight to said light sensing means for the electrical control thereof.